1251501881557 has 2 divisors, whose sum is σ = 1251501881558. Its totient is φ = 1251501881556.

The previous prime is 1251501881503. The next prime is 1251501881633. The reversal of 1251501881557 is 7551881051521.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 633885076561 + 617616804996 = 796169^2 + 785886^2 .

It is an emirp because it is prime and its reverse (7551881051521) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1251501881557 is a prime.

It is a super-2 number, since 2×1251501881557² (a number of 25 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1251501881557.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1251501881057) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 625750940778 + 625750940779.

It is an arithmetic number, because the mean of its divisors is an integer number (625750940779).

Almost surely, 2^{1251501881557} is an apocalyptic number.

It is an amenable number.

1251501881557 is a deficient number, since it is larger than the sum of its proper divisors (1).

1251501881557 is an equidigital number, since it uses as much as digits as its factorization.

1251501881557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 560000, while the sum is 49.

The spelling of 1251501881557 in words is "one trillion, two hundred fifty-one billion, five hundred one million, eight hundred eighty-one thousand, five hundred fifty-seven".